After another rough start, are Justin Verlander's days as an ace over?

Justin Verlander was arguably the best pitcher in baseball just two years ago, and the year before that, he became the first starting pitcher in a quarter century to win his league's Most Valuable Player award. But after Thursday's loss to Toronto, there are reasons to believe that these most recent struggles indicate that the 31-year-old Verlander's days of dominance are behind him.

In giving up six runs in seven innings in Detroit's 7-3 loss to the Blue Jays, Verlander allowed five or more runs for the fourth time in his last five starts. The last time that happened was all the way back in July and August of 2008, the only sub-par season of his otherwise outstanding career. Thursday's start was a slog all around for Verlander, as he struck out just four batters, walked four and gave up two homers. It's the seventh time in 13 starts this year that Verlander has struck out four or fewer batters in a game, something he did only 10 times in 34 starts last season and only five times in 33 starts in 2012. On top of that, Verlander notched just seven swings-and-misses in his 107 offerings Thursday, including only two whiffs on his 48 four-seam fastballs.

Although he never struggled to quite this degree last season, Verlander was clearly diminished early in 2013 as well, with a drop in velocity and an increase in his walk rate reducing his effectiveness. A strong finish to the season, however, provided hope that he could recapture his Cy Young form this season. Over his last five starts in 2013, three of which occurred in the postseason, Verlander allowed just one run in 35 innings while striking out 52 against just seven walks, getting his velocity back up near his 2011 level.

That run of success now looks like a last gasp of greatness from a pitcher who, with the postseason included, led the majors in innings pitched from 2009 to 2012, averaging 250 innings per year in games that counted. Not only is his velocity back down this season, but his strikeout rate has also gone with it, while his walks are back up, all negative indicators that suggest that Verlander is either hurt or simply not the same pitcher he was two years ago and may never be again.

During his four-year peak, Verlander's average fastball fell just shy of 96 miles per hour. He was throwing almost that hard in those final five starts last year, and has shown flashes of that old velocity this season, but in his first dozen starts of 2014 combined (not including Thursday's outing), his fastball averaged under 94. Meanwhile, with Thursday's start included, he has struck out just 6.4 men per nine innings this season, down from 8.9 in the last four seasons combined, and has walked 3.7 per nine, up from 2.4 BB/9 in his four peak seasons.

This is a depressingly familiar sight. Two of the other dominant workhorses of the last decade have preceded Verlander into collapse in the last few seasons. Roy Halladay, who, including the postseason, averaged just shy of 252 innings per season from 2008 to 2011, saw his velocity drop by two miles per hour in 2012, signaling shoulder problems which ended his career the next year. CC Sabathia, who averaged just shy of 256 innings per year from 2007 to 2011 (again, postseason included), saw his velocity start to erode in 2012, shedding more than two miles per hour from 2011 to 2013 and averaging just 90.8 miles per hour on his fastball this season (down four mph from his peak). As with Halladay, that velocity drop anticipated a drop in effectiveness and increasing fragility. Sabathia is currently on the disabled list with a degenerative knee issue that is expected to keep him on the shelf through July, freezing his season ERA at 5.28 after eight starts.

Neither of those pitchers was particularly old. Halladay was 35 in 2012, and Sabathia was just 32 last year when he posted a 4.78 ERA, while Verlander is only 31 and has yet to hit the disabled list in his career. He did have offseason surgery to repair a torn abdominal muscle, but there has been no indication from Verlander thus far that he has had any lingering issues stemming from that surgery.

That said, he's clearly not right. If it were only a few rough starts with his usual velocity and peripherals, it would be easy enough for the Tigers to shrug it off as a random rough patch given their first-place standing and soft division. However, given the very real performance changes behind his struggles and the $140 million Detroit still owes him over the next five years, the Tigers may want to take his current struggles as a warning sign and find an excuse to give Verlander some time off, be it via a vaguely-worded disabled list stay, or simply by skipping a start here or there.

Lest you think I'm overreacting, the last time I made a suggestion like that about a star pitcher was almost exactly two years ago, when I suggested the Giants find a way to give Tim Lincecum a breather following a similar drop in velocity and control. The Giants never did, and while an injury never surfaced, Lincecum never recovered, either. That's not to imply that a rest in June 2012 would have changed the course of Lincecum's career, but the performance changes detected then did indeed prove to be real and lasting. I hate to say it, but the same seems very likely to be true for Verlander, as well.